Injection Molding

Question 1

What influences the final tolerance of an injection molded part?

Answer 1

Polymer, Fillers, Mold Geometry, and Processing Conditions

Question 2

What is the order of thickness shrinkage for a filled and unfilled injection molded
part?

Answer 2

Filled = 10/1000 - 100/1000
Unfilled= 1/1000 - 10/1000

Question 3

. What does a basic mold in an injection molder consist of?

Answer 3

A cavity and a core plate

Question 4

. Why are simple mold shapes typically used in injection molders?

Answer 4

To reduce cooling costs

Question 5

How far through the wall of a part can holes be molded?

Answer 5

2/3 of the way through the wall

Question 6

Why are drills used to complete holes in injection molded parts?

Answer 6

In order to eliminate weld lines

Question 7

What are the three machine types for an injection molder?

Answer 7

Hydro, electric, hydroelectric

Question 8

. What is the benefit of an all-electric injection molder machine?

Answer 8

Very low fixed energy costs

Question 9

What type of warping can occur with injection through diagonal gates?

Answer 9

Twisting

Question 10

What is the minimum wall thickness required for an injection molded part?

Answer 10

.025 in

Question 11

Describe the processing window that Inj. Molding must operate within

Answer 11

Temperature vs. Pressure, involving how the polymer will either shortshot, melt,
Flash, or Degrade beyond limits. Varies with different thermoplastic materials.

Question 12

What are sink marks and weld lines with respect to Injection molding?

Answer 12

Weld lines are where two or more molten thermoplastic flows meet within a mold
creating micro seam within the solidified part (generally a little weak
cohesiveness. Sink marks are defects where greater polymer shrinkage has
occurred opposite to non-uniform surface features, such as ribbing and joints.

Question 13

Why are draft angles important?

Answer 13

To allow for easier part removal